Recent years have seen numerous kinds of apparatus developed and marketed as video signal sources. For example, ordinary television sets are equipped with many video input terminals for receiving video signals from a video tape recorder (VTR) and optical disk players in addition to broadcast program signals.
The characteristics of the video signal of VTR's sometimes differ from those of optical-disk players (commonly known as laser disk players). For example, the frequency characteristic of the video signal may vary depending on the performance and property of the video apparatus in question. Furthermore, recordings are sometimes made on the medium in such a manner that special visual effects are provided to enhance the contents of the program recorded.
Given these parameters of variation, a video apparatus with fixed video circuit characteristics such as a conventional television sets may not cope sufficiently with diverse video signals coming from external video sources. For example, the screen may turn high-resolution pictures into scenes of unnatural glare, or the screen may show "dulled" pictures lacking visual sharpness.